Epsilon Eridaini is a sun like star found only 10 light years away. Scientists believe that it may have a planet orbiting it. The planet can only be seen by its gravitational wobble.


Facts about Epsilon Eridaini

Spectral class:K2V

Distance from earth: 10.8

Luminosity: 0.3L

Mass: 0.7 solar masses

Surface temperature: 5200 Kelvin

Lifetime: 15billion years

Type of star: Orange Dwarf

Habitable Zone: 0.4-0.6 AU

                                                                                Comparison to our solar system



Main sequence stars of spectral type K are slightly smaller, less massive and cooler than our sun. The second most common stars within the galaxy, they have a longer lifetime, and their ecosphere is narrower and also closer to the star.


Epsilon Eridani is an excellent candidate for extraterrestrial life. Though it is a star of spectral type K, it is still very similar to our own sun. An Earth-sized planet may still have an acceptable climate. Epsilon Eridani does not have any stellar companions, which could have disturbed the formation of planets. This star was among the first targets for Frank Drake's first run of SETI in 1960, and future generations of telescopes should settle the question of life at Epsilon Eridani very soon, within the next few decades. As a prerequisite for planets, a faint disk of dust of 60 AU radius has been detected around Epsilon Eridani.

Reports of a Planet Around Epsilon Eridani

The evidence for a planet around Epsilon Eridani was first reported by Bruce Campbell, Gordon Walker, and Stevenson Yang (Campbell et al. 1988). Their Doppler measurements suggested a companion mass of 1.2-4.7 times the mass of Jupiter (see their Table 3). Campbell's planet around Epsilon Eriaini remained controversial, as more velocity measurements were needed, along with a better understanding of the noise from the star. In 1999, Andrew Cumming, G. Marcy, and P.Butler reported a clear periodicity in the Doppler measurements from Lick Observatory (Cumming et al. 1999). The probability of a false alarm was 0.002. The period was 6.9 yr., and the implied mass resided at the low end of that which Campbell et al. had reported, and certainly in agreement.

Doppler measurements at McDonald Observatory obtained by Bill Cochran and Artie Hatzes were reported at the International Astronomical Union in August, 2000, which agree with the previous reports by Campbell et al. and Cumming et al.

Dr. Sallie Baliunas has supplied chromospheric measurements of Epsilon Eriidaini which exhibit no apparent periodicity in the chromosphere near 6.9 yr. This has been interpreted as supporting evidence that Campbell's planet is real, rather than an artifact of the magnetically active star.

However, the Doppler behavior of magnetically active stars remains poorly explored, because so few stars are as active as Epsilon Eridani. Thus, Campbell's interpretation of a planet remains controversial.

A graph to show the gravitational wobble of the star and its planet proving the existence of a planet


The best and most popular picture of epsilon eridaini 

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By Ross Harding aged 13